The present invention relates broadly to vehicular transmissions. In general, the present invention relates to two-mode, compound-split, vehicular transmissions. More particularly, the present invention relates to two-mode, compound-split, vehicular transmissions that utilize supplemental power receiving/delivery units that may derive their power either directly or indirectly from the vehicle engine and selectively impart it to compounded planetary gear subsets in the transmission. Specifically, the present invention relates to a two-mode, compound-split, electromechanical, vehicular transmission wherein the interactive planetary gear arrangements that are operatively connected to an engine and two power receiving/delivery unitsxe2x80x94motor/generators, as shownxe2x80x94that may be annularly configured. The planetary gear arrangements as well as the two motor/generators are disposed coaxially with the planetary gear arrangements located radially inwardly of the motor/generators. The rotatable members in the planetary gear subsets and the motor/generators are supported either directly by the transmission housing or indirectly by the transmission housing through a transmission main shaft that is also coaxially disposed relative to the aforesaid transmission components such that the rotating components which might otherwise induce undesirable vibrations are laterally grounded to minimize such vibrations.
The purpose of a vehicular transmission is to provide a neutral, at least one reverse and one or more forward driving ranges that impart power from an engine, and/or other power sources, to the drive members which deliver the tractive effort from the vehicle to the terrain over which the vehicle is being driven.
As explained in detail in U.S. Pat. No. 5,931,757, the challenge is to provide a power system that will operate at high efficiencies over a wide variety of operating conditions. Desirable electric variable transmissions should leverage not only the benefits of a series, hybrid transmission for desirable low-average power duty cyclesxe2x80x94i.e.: low speed start/stop duty cyclesxe2x80x94but also the benefits of a parallel hybrid transmission for high-average output power, high speed duty cycles.
In a parallel arrangement the power supplied by the engine and the power supplied by the source of electrical energy are independently connected to the drive members. Perfecting a concept wherein two modes, or gear trains, are available for synchronous selection by the on-board computer to transmit power from the engine and/or selected motor/generators to the output shaft results in a hybrid transmission having an extremely wide range of applications, and the most desirable of the beneficial results may be achieved by the use of a variable, two-mode, input-split, parallel, hybrid electro-mechanical transmission.
With reference, again, to a simple planetary gear set, the planet gear members are normally supported for rotation on a carrier that is itself rotatable. When the sun gear is held stationary and power is applied to the ring gear, the planet gear members rotate in response to the power applied to the ring gear and thus xe2x80x9cwalkxe2x80x9d circumferentially about the fixed sun gear to effect rotation of the carrier in the same direction as the direction in which the ring gear is being rotated.
However, when any two members of a simple planetary gear set rotate in the same direction and at the same speed, the third member is forced to turn at the same speed, and in the same direction. For example, when the sun gear and the ring gear rotate in the same direction, and at the same speed, the planet gears do not rotate about their own axes but rather act as wedges to effect rotation of the carrier with the sun and ring gears.
When the two gear members rotate in the same direction, but at different speeds, the direction in which the third gear member rotates may often be determined simply by visual analysis, but in many situations the direction will not be obvious and can only be determined by knowing the number of teeth present in the gear members of the planetary gear set.
Whenever the carrier is restrained from spinning freely, and power is applied to either the sun gear or the ring gear, the planet gear members act as idlers. In that way the driven member is rotated in the opposite direction as the drive member. Thus, in many transmission arrangements when the reverse drive range is selected, a torque transfer device serving as a brake is actuated frictionally to engage the carrier and thereby restrain it against rotation so that power applied to the sun gear will turn the ring gear in the opposite direction. Thus, if the ring gear is operatively connected to the drive wheels of a vehicle, such an arrangement is capable of reversing the rotational direction of the drive wheels, and thereby reversing the direction of the vehicle itself.
The aforesaid U.S. Pat. No. 5,931,757 teaches those skilled in the art that when the variable, two mode, input-split, parallel, hybrid electro-mechanical transmission as well as the two motor/generators are coaxially disposed and the motor/generators are each configured as an annulus, the motor/generators may circumscribe one or more of the planetary gear arrangements such that the planetary gear arrangements are disposed radially inwardly of the motor/generators.
However, if careful attention is not given to the configuration and placement of the supports for at least the more massive of the various rotating membersxe2x80x94i.e.: the sun gear, the ring gear, the carrier and/or the rotors of the motor/generatorsxe2x80x94undesirable vibrations may be induced. Historically, for example, the mass of the planetary gear subsets and the mass of the circumscribing rotors in the motor/generators were supported solely the rotor bearings. While efficient, this arrangement does not necessarily preclude the vibrations induced by rotation of the aforesaid masses.
It is, therefore, one primary aspect of the present invention to provide an improved and novel, two-mode, compound-split, transmission incorporating supplemental power receiving/delivery units in such a way that the transmission is enhanced by reduced vibrations.
It is another aspect of the present invention to provide a novel, two-mode, compound-split, electro-mechanical transmission, as above, wherein the transmission employs a main shaft that is rotatably supported from the rigid transmission housing so as to reduce vibrations.
It is a further aspect of the present invention to provide a novel, two-mode, compound-split, electro-mechanical transmission, as above, wherein the rotors of the motor/generators utilized to provide the supplemental power receiving/delivery units are supported from the transmission housing in such a manner as to minimize vibrations.
It is still another aspect of the present invention to provide a novel, two-mode, compound-split, electro-mechanical transmission, as above, wherein the planet gears of at least selected planetary gear subsets are incased in a uniquely configured cage-like carrier that is rotatably supported from the rigid, transmission housing through the transmission main shaft so as to minimize vibrations.
These and other aspects of the invention, as well as the advantages thereof over existing and prior art forms, which will be apparent in view of the following detailed specification, are accomplished by means hereinafter described and claimed.
By way of a general introductory description, a two-mode, compound-split, electro-mechanical transmission embodying the concepts of the present invention utilizes an input member for receiving power from a prime mover power source and an output member for delivering power from the transmission. The transmission utilizes a plurality of planetary gear subsets that circumscribe a transmission main shaft which extends axially within the transmission and at least selective of the aforesaid planetary gear subsets are, in turn, circumscribed by first and second motor/generators.
Unique structural means are employed to ground the various rotating members in order to preclude them from lateral movement while not interfering with their desired rotation.
Selected planetary gear subsets may also employ uniquely configured carrier cage assemblies that assure the necessary meshing engagement of the planet gears supported therein with the outer ring gear and the inner sun gear of the planetary gear subsets within which the unique carrier cage assemblies are associated. The unique configurations of the carrier cage assemblies not only preclude lateral movement thereof, but also movement of the planet gears supported therein in directions other than that of their respectively desired rotation.
To acquaint persons skilled in the arts most closely related to the present invention, one representative preferred embodiment of a two-mode, compound-split, electro-mechanical transmission now contemplated for putting the invention into practice is described herein by, and with reference to, the annexed drawings that form a part of the specification.
It must be understood that the aforesaid exemplary form of a preferred two-mode, compound-split, electro-mechanical transmission is described in detail without attempting to show all of the various forms and modifications of the essential elements in which the invention might be embodied.
As such, the embodiment shown and described herein is only illustrative, and as will become apparent to those skilled in these arts can be modified in numerous ways within the spirit and scope of the invention; the invention being measured by the appended claims and not by the details of the specification.